From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8C3CC28EBD for ; Sun, 9 Jun 2019 09:37:26 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 32C9A208E4 for ; Sun, 9 Jun 2019 09:37:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 32C9A208E4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8CB8A4A4F8; Sun, 9 Jun 2019 05:37:25 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id N74j2MVvAQt0; Sun, 9 Jun 2019 05:37:24 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 85BB84A512; Sun, 9 Jun 2019 05:37:24 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 9D7F94A50C for ; Sun, 9 Jun 2019 05:37:23 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id kviPCiitzQBF for ; Sun, 9 Jun 2019 05:37:22 -0400 (EDT) Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 47D364A4F9 for ; Sun, 9 Jun 2019 05:37:22 -0400 (EDT) Received: by mail-wm1-f52.google.com with SMTP id c66so5805896wmf.0 for ; Sun, 09 Jun 2019 02:37:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=N/JT6wxx8SnEUHFdFMXDjIDadpkBg6G764joNYPh7l8=; b=DnQToNskziR/Dien1HkZBccjZvYJyaqtfaTJw61GvHU96KYmblJ2EceyFeQvgk5t3Q MofCamnL19fc1e0ddEZW0UInPXjJu13I+/SebXkCUtrIPCktdaqmIiOZt67OvTMJ6Wo3 vuDoG04/Hm2HtxsKePf0OhceTZioHcKwo1WXP43hR5gmO3Mi8nPMH3jSWhXlzzTKMhDP kp4Qy/HO5fuJ8cE3y0PyQLc7LMEUcjIfqLAKFuNDbJAFKncXk/CdkoMeAomLpHncCiER laD8zhuYteHHua5T43Snt2uwHYYKS7Hx/KZDLdjA4vVODu6hPCIe7yqVsf+g/X56pxID C9Kg== X-Gm-Message-State: APjAAAXx3lZXKuzwaXBm1/3c59UUiOAUSXKRekF8Q8uGqoUApdb67msz fxlRLemfaqbAF13eKI8JOtAIj1EurCY= X-Google-Smtp-Source: APXvYqyAtJD90KBreJ8YMy512INUJXccvzCGcpA/XJQQf/F7Ze/ETljJlq57FHnss/Ayp0CtUHfiww== X-Received: by 2002:a1c:7d56:: with SMTP id y83mr9949310wmc.77.1560073041026; Sun, 09 Jun 2019 02:37:21 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:8cc3:8abd:4519:2cd6? ([2001:b07:6468:f312:8cc3:8abd:4519:2cd6]) by smtp.gmail.com with ESMTPSA id b5sm7097123wru.69.2019.06.09.02.37.20 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Sun, 09 Jun 2019 02:37:20 -0700 (PDT) Subject: Re: Reference count on pages held in secondary MMUs To: Christoffer Dall , kvm@vger.kernel.org References: <20190609081805.GC21798@e113682-lin.lund.arm.com> From: Paolo Bonzini Message-ID: <3ca445bb-0f48-3e39-c371-dd197375c966@redhat.com> Date: Sun, 9 Jun 2019 11:37:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190609081805.GC21798@e113682-lin.lund.arm.com> Content-Language: en-US Cc: kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On 09/06/19 10:18, Christoffer Dall wrote: > In some sense, we are thus maintaining a 'hidden', or internal, > reference to the page, which is not counted anywhere. > > I am wondering if it would be equally valid to take a reference on the > page, and remove that reference when unmapping via MMU notifiers, and if > so, if there would be any advantages/drawbacks in doing so? If I understand correctly, I think the MMU notifier would not fire if you took an actual reference; the page would be pinned in memory and could not be swapped out. Paolo _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm